Promotion of Oxygen Reduction with Both Amorphous and Crystalline MnO_x through the Surface Engineering of La_0.8Sr_0.2MnO_3‐δ Perovskite

Abstract

Surfaces play a key role in catalysis. Surfaces can be modified in a number of ways, for example by depositing nanoparticles or with functional coating layers. Here, the surface of La0.8Sr0.2MnO3‐δ (LSMO) is treated with diluted HNO3. This process leads to the preferential formation of MnOx/LSMO on the surface, leading to the exposure of Mn cations at the surface of LSMO. The electrocatalytic activity of the MnOx/LSMO heterostructure towards the oxygen reduction reaction (ORR) is shown to increase when it is compared to the untreated LSMO. Thanks to the formation of MnOx at the surface, the resulting MnOx/LSMO possesses 1) a relatively high specific surface area and a mesoporous structure, 2) a higher coverage of Mn4+/Mn3+ cations at the surface, and 3) a high concentration of highly oxidative oxygen species. This work develops a facile strategy (i. e. HNO3 treatment) for improving the ORR activity of perovskite oxides in alkaline solution at room temperature.

Recent Advances in Perovskite‐Type Oxides for Energy Conversion and Storage Applications

“…As a catalyst for hybrid Li–air batteries, this material shows excellent electrochemical performance and stability. Yu et al [ 208 ] treated the surface of La 0.8 Sr 0.2 MnO 3– δ (LSMO) using diluted HNO 3 . Thus, MnO x formed on the surface of LSMO and more Mn cations were exposed.…”

Unlocking the Potential of Mechanochemical Coupling: Boosting the Oxygen Evolution Reaction by Mating Proton Acceptors with Electron Donors

“…From the Co 2p spectra given in Figure a,b, we can observe the Co 2p 3/2 and Co 2p 1/2 orbitals in MoS 2 @SCO B have a shoulder at higher binding energies compared to those in SCO B , implying an increased oxidation state of Co. [ 26 ] Figure 4c,d shows the O 1s spectrum of SCO B and MoS 2 @SCO B , which is fitted to four peaks corresponding to oxygen from surface‐adsorbed water (533 eV), the hydroxyl group (531.1 eV), superoxidative oxygen (530.15 eV), and lattice oxygen (528.8 eV). [ 27 ] Compared to SCO B , the MoS 2 @SCO B spectrum has a higher peak of superoxidative oxygen, which suggests the presence of superoxide and peroxide species (O 2 2− /O − ) on the catalyst surface. [ 28 ] The area underlying the superoxidative oxygen peak accounts for 28% of the total O 1s area in MoS 2 @SCO B .…”

Oxygen Reduction Reaction Electrocatalysis in Alkaline Electrolyte on Glassy-Carbon-Supported Nanostructured Pr6O11 Thin-Films

“…The ORR activity of the crystalline Pr 6 O 11 sample was better than that of the as-prepared one ( Figure 9A), as clearly revealed when directly superposing the two sets of data on the same axes ( Figure 9B). While the onset potential value (E onset = 0.835 V vs RHE, in the average for such class of materials [46,[75][76][77][78][79][80][81], although in these papers, the materials were tested with carbon as electron-conductive additive) was barely changed compared to the amorphous sample, the limiting current plateaus were better defined. However, they still do not match the expected values for a 4-electron ORR, by a factor ca.…”

“…The importance of the crystalline nature of the perovskites has been ascertained, with smaller crystals yielding larger ORR activity [44]. The influence of the facets has also been put forth [45] as well as the crystalline versus amorphous nature of the oxide [46,47], but in these cases, composite electrodes using carbon additives were used.…”